In many semiconductor applications, semiconductor devices have relatively high integration (e.g. the size of the semiconductor devices may be relatively small and an arrangement density of the semiconductor device is relatively high). Accordingly, critical dimensions of a mask pattern corresponding to relatively small semiconductor device may approach the resolution limit of an optical exposure apparatus.
A method of optical proximity correction (OPC) may be used to overcome the difficulties in photolithography processes. A method of OPC may include at least one of the following: Manufacturing a mask pattern for a test using a test pattern representing all patterns in a design. Transferring a pattern to a semiconductor substrate using the mask pattern. Performing etching to form a semiconductor pattern for a test on the semiconductor substrate.
An ArF light source used in a photolithography process may have a wavelength of approximately 193 nm, which may cause complications. An ArF light source may have a relatively small polymer adsorption force, which may result in a relatively low resistance to plasma. The reactivity to an etchant may be relatively high to an ArF light source, which may result in a relatively low etch margin, which may compromise the uniformity in critical dimension of the semiconductor substrate.
In order to overcome complications with ArF light sources, etching methods using trimming technology may be used to control etching time when a critical dimension in a design is larger than a desired real dimension in forming a pattern. However, when trimming technology is used, it may be relatively difficult to control etching time. As a result, differences between critical dimensions may easily occur when forming micro patterns. Accordingly, it may still be difficult to have a reasonably repeatable process margin when using optical proximity correction.
Achieving adequate micro line width resolution may be difficult based on a micro-scale reduction of a design line width. Micro-scale reduction of a pattern may be complicated because the resolution of the cell pattern is affected by an optical proximity effect, where a line width of a line end is diminished. As a result, a margin of a line end of a mask pattern for a gate pattern with respect to a mask pattern for an active region may not be accurately formed, which my compromise cell operation characteristics.
For example, if a cell area is less than approximately 130 nm, it may be difficult to form a line end with appropriate dimensions. Example FIG. 1A illustrates line ends A and B for mask pattern 2 for a gate pattern in an active region that are straight with respect to mask pattern 1 for an active region. Example FIG. 1B illustrates line ends C and D of mask pattern 2 for a gate pattern bent with respect to mask pattern 1 for an active region. Line ends C, and D that are bent may be relatively difficult to form when a cell area is less than approximately 130 nm.
However, when the spatial margin is not sufficient to bend line ends as illustrated in example FIG. 1C, the line ends of mask pattern 2 for a gate pattern may be pointed like a spear with respect to mask pattern 1 for an active region. As a result, the edge length in the direction a may be similar to the edge length in the direction β, which may result in accelerated line-end shortening (LES). Accordingly, it may be difficult to accomplish a desired image pattern, even though an OPC process is performed on line ends of mask pattern 2 for a gate pattern.